Not much new about Japanese beetles | Outside

Japanese beetles were first found in Minnesota in 1968, but were thought to be abundant around 2011 as they invaded the Twin Cities area in droves. Now, there may be some dispute over these dates, but suffice it to say that they have been a major headache for gardeners for a long, long time. And they will continue to be with us for – well maybe forever, unless some very welcome natural predator, some safe insecticide, or some miracle happens to rid us of this annoying pest.

Japanese beetles or Popillia japonica are not yet found in all counties in Minnesota. But before you think about moving to a “safer” county so you can garden with the peace of mind of not fighting Japanese beetles, you might want to stay put for now. A Minnesota Department of Agriculture search online has a map showing which counties are affected and which areas have not yet been. I think if you want to move to say, Warrod, Minnesota, you might be safe for a few years. Keep in mind that what you can grow here in the Twin Cities and surrounding areas is not quite the same as what you can successfully grow in the northernmost counties of our state.

the minnesotaseasons.com The website has a good map of where these pests have been found in our state. As of 2020, the Seven Counties metropolitan area is teeming with Japanese beetles with large numbers also in the Winona and Rochester areas. But for the purposes of this article, let’s just say that they’re here in abundance and are a headache for anyone gardening. And their peak period usually runs from late June through August, with July being the busiest.

Without a doubt, as a master gardener in Chisago County, the question about all things Japanese beetles is the most frequently asked question I receive. I can answer that one in my sleep. But rather than struggling to find an answer that will appease the client, I prefer to educate them on some of the most important things to understand about this pest. Like what plants they prefer and what plants you might want to add to your landscape that will deter them from your roses. Or the art of “handpicking” them from your plants. Drop them in a bucket of soapy water and I guarantee they will die! In other words, how to live and garden with this pest that will not die or move to another area. And even if they did, I’m pretty sure another villain is waiting just around the corner in the evolution.

And before you ask, no. Even the coldest Minnesota winter won’t freeze the Japanese beetle to extinction. They are simply too well adapted to our conditions for the larva that overwinters underground to have any chance of developing into a beetle. Some research I’ve read indicates that there are larval deaths, but not enough to reduce their numbers.

During these still very cold winter days, you might want to spend some time on the internet to learn more about Japanese beetles and how you can still successfully grow a beautiful and productive garden. Understanding this pest won’t make it go away, but it will help you make the right choices for your gardens.

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